1. Field of the Invention
The present invention relates to exposure apparatuses and device manufacturing methods, and more particularly to an exposure apparatus that exposes an object with an energy beam via an optical system, and a device manufacturing method that uses the exposure apparatus.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (integrated circuits or the like) or liquid crystal display elements, an exposure apparatus such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper), or a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner)) is mainly used.
In this type of the projection exposure apparatus, a stage device that accurately drives a stage that moves along a predetermined two-dimensional plane while holding a wafer is provided, in order to overlay and form device patterns on a substrate such as a wafer or a glass plate (hereinafter, generically referred to as a wafer). In this case, in order to improve the throughput, it is required for the stage device to drive the stage at high speed with high acceleration. Therefore, for example, as disclosed in U.S. Pat. No. 6,437,463, a stage device has been developed that has a configuration of driving a stage using a planar motor by an electromagnetic force drive method. Incidentally, the planar motor is configured of a stator arranged in a surface plate that holds the stage and a mover arranged in the stage.
Furthermore, it is required for the stage device to position a wafer with respect to the device patterns with high precision by driving the stage such that device patters are overlaid and formed with high precision. Therefore, in order to respond to such requirement, for example, in the fifth embodiment of U.S. Patent Application Publication No. 2008/0094594, a two-dimensional encoder system is enclosed that measures positional information of a stage by irradiating a grating arranged at the stage with a measurement beam from directly below and receiving reflected/diffracted light from the grating. In the two-dimensional encoder system related to the fifth embodiment of U.S. Patent Application Publication No. 2008/0094594, a two-dimensional encoder (a head section that emits the measurement beam) is fixed to a surface plate that supports the stage. Therefore, if the two-dimensional encoder system described in U.S. Patent Application Publication No. 2008/0094594 is applied to the previously-described stage device (U.S. Pat. No. 6,437,463) having a configuration that uses the planar motor without any changes, a reaction force accompanying a drive force used to drive the stage causes vibration of the surface plate at which the two-dimensional encoder (head section) is arranged, thereby the measurement accuracy of the two-dimensional encoder system is degraded, and as a consequence, there is a risk that the position control accuracy is degraded.